This invention relates to a method of estimating ingredients of liquefaction products of coal or its analogues from a resonance spectrum thereof obtained using a solid state .sup.13 C nuclear magnetic resonance spectrometer.
Coals are more widely spread in the world as compared with petroleum and natural gas. The estimated amount of available coal deposits is about 1 trillion tons. These fossil resources are estimated to be recoverable for another 216 years for coal, 46 years for petroleum and 64 years for natural gas, and it is considered that these fossil resources will be important energy resources for human society as ever. At present, about one third of the amount of the primary energy consumed in the world is dependent on coal, and approximately 120 Mt/y of coal is consumed in the steel industry and the field of electric power generation in Japan.
It is known, however, that coal generates more carbon dioxide per unit heating value than petroleum and natural gas and also generates a large quantity of sulfur dioxide, nitrogen dioxide, soot out dust and so on. Therefore, in order to utilize coal resources with the consideration of the protection of environment, it is necessary to develop an energy-efficient and low-emission coal conversion technology. For example, in the field of the environmentally friendly electric power generation, technologies for pressurized fluidized bed combined power generation and coal gasification combined cycle power generation are under development with the aim of improving generation efficiency. In the steel industry, the development of a new technology for producing coke for iron manufacturing is in progress.
On the other hand, it is expected that petroleum will be in short supply with respect to increasing demand thereof in the near future. Then, a coal liquefaction technology for producing gasoline and light oil from coal has been promoted as a technology for manufacturing substitute fuel for petroleum, and, as a consequence, NEDOL process has been established. At present, technology transfer of the process to countries, such as Indonesia and China, that are making remarkable economic growth and suffering from energy shortage, is under consideration.
The main elements of coal are carbon, hydrogen and oxygen, and the chemical structure thereof is characterized in that structural units consisting of condensed polycyclic aromatic compounds having various numbers of rings are linked to each other through methylene crosslinks or ether bonds to form chemically inconsistent polymeric structure. Heteroatoms such as oxygen, sulfur and nitrogen exist as various functional groups bonded around aromatic rings with an alkyl side chain or as heterocyclic compounds in which they are incorporated within rings. Generally, as the rank of coalification proceeds from brown coal to bituminous coal, the proportion of condensed polycyclic aromatic compounds contained therein increases and the chemical structure thereof continuously changes and tend to be stabilized chemically. Additionally, coal typically contains approximately a few to 30% of ashes, which can be a cause of troubles such as abrasion of the equipment and clogging by fusion in coal utilization processes.
A liquefaction reaction of coal is a conversion reaction technology as a technology of manufacturing substitute fuel for petroleum from coal aiming at manufacture of liquid transportation fuels such as gasoline and light oil. In contrast to combustion or gasification, which occurs at high temperature beyond 800.degree. C., a liquefaction reaction decomposes coal under high-pressure hydrogen of 10 to 25 Mpa, and under a mild reaction condition of a temperature of 430 to 470.degree. C., to produce oil which is a mixture of low molecular weight aromatic and aliphatic hydrocarbon. The reaction starts with cleavage of crosslinks between structural units and functional groups with low bonding energy, and then goes to the decomposition into smaller molecules of preasphaltene and asphaltene fractions. There follows the formation of cycloparaffin and its analogues and ring-opening reactions thereof into lower molecular weight substances by hydrogenation of aromatic rings, thereby producing oils along with gases. Thus, it is known from basic studies in the past that liquefaction reactivity of coal is strongly influenced by the chemical structure thereof, i.e. the proportion of aromatic ring structures and crosslinks, the quantity of oxygen-containing functional groups and so on.
After the "oil crisis" in 1973, development researches on the coal liquefaction technology were vigorously pursued as a national project aiming at decrease of dependence on petroleum and diversification of energy resources in Japan. As a result, the liquefaction technology in Japan established NEDOL process with the highest performance in the world through a test operation using a 1 t/d process--supporting apparatus and a 150 t/d pilot plant. The process is designed to be applicable to a wide variety of coals from sub-bituminous coal to bituminous coal in consideration of the energy situation in Japan in which coal resource also must be imported from abroad and is a technologically and economically advanced liquefaction technology peculiar to Japan. Liquefied oil can be produced under mild reaction conditions with a high yield by employing an iron-based particulate catalyst and hydrogen donor solvent. The typical reaction conditions thereof involve a reaction temperature of 440 to 470.degree. C., a reaction pressure of 15 to 20 Mpa, a concentration of coal slurry of 40 to 50%, an amount of added catalyst of 1.5 to 3% and a gas/liquid ratio of 0.7 to 1.0 Nm.sup.3 /kg. As a result, an oil yield (boiling point: C.sub.4 to 350.degree. C. fraction) between 50 and 60 wt % (about 4 barrels per 1 ton of coal) can be obtained.
At present, at the request from Indonesia and China, feasibility studies on transferring the process to those countries are now conducted and it is expected to contribute greatly to stabilized energy supply in Asian countries.
As mentioned before, liquefaction reactivity of coal is highly dependent on the chemical structure thereof, i.e. the type of the coal so that yields of oil and other products vary according to the type of the coal. In order to obtain a high yield of oil, on which the cost effectiveness of the process depends, an optimum reaction condition of each type of coal must be discovered. For that purpose, however, it is necessary to carry out reaction tests in a plant and a large amount of costs, efforts and time is required to obtain reaction data of each coal. That is the reason why a convenient method of estimating reactivity has long been desired.
In spite of this, no suitable method to determine chemical structure of coal had been established. However, a solid state .sup.13 C nuclear magnetic resonance spectrometer was recently developed and it has become possible to measure carbon distribution of coal. Although the instrument cannot directly determine distribution of a variety of chemical structures of coal, it shows carbon distribution corresponding to an average chemical structure of coal, which leads to a conclusion that there must be a close relation between carbon distribution and reactivity.
However, no appropriate method of analyzing spectral data of coal to determine a correlation between carbon distribution and liquefaction reactivity of coal has been established yet. Also, most of the reaction tests to determine liquefaction reactivity are carried out by using small-scale batch-type autoclaves so that obtaining quantitative reaction data under a steady condition has been very limited. Under these constraints, it was virtually impossible to find out a correlation between chemical structure of coal and liquefaction reactivity thereof with high accuracy.